Apparatus for co-curing composite skins and stiffeners in an autoclave

ABSTRACT

A composite skin and composite stiffeners are co-cured in an autoclave. Uncured stiffeners are placed in channels of a tool, and an uncured skin is placed on the tool contacting the stiffeners. The vacuum bag is sealed over the tool. Bladders placed in the stiffeners are exposed to autoclave pressure through a manifold system employing vent tubes that pass through the vacuum bag along a side of the tool.

BACKGROUND INFORMATION

1. Field

This disclosure generally relates to manufacturing composite parts, anddeals more particularly with a method and apparatus for co-curingcomposite skins and stiffeners in an autoclave.

2. Background

It is sometimes necessary to cure multiple composite parts in anautoclave which require internal bladders to prevent them fromcollapsing under autoclave pressure. For example, in the aircraftindustry, a composite skin may be compressed against and co-cured withmultiple stiffeners having a hat shaped cross-section using a vacuum bagand autoclave pressure. In order to avoid collapsing under the autoclavepressure, the bladders may be vented to the autoclave environment sothat the internal pressure in the bladders is substantially that appliedby the autoclave. One technique for venting the bladders is to placeholes in the bladders which are vented through the vacuum bag. Ventingthe bladders through the vacuum bag increases the possibility of leakageinto the bag, and can also lead to undesirable pre-loading of ventpipes, as well as potential distortion of fiber stiffeners duringcuring, and possible resin starvation issues.

It would be desirable to provide a method and apparatus for co-curingcomposite skins and stiffeners which avoid the need for venting thebladders through the vacuum bag while promoting substantially evendistribution of autoclave pressure to the bladders. There is also a needfor apparatus as described above which may be easily reconfigured foruse with differing types of part assemblies.

SUMMARY

The disclosed embodiments provide a method and apparatus fordistributing autoclave pressure to an array of a bladders in order tocompact fiber reinforced resin stiffeners during an autoclave curecycle. A manifold system distributes autoclave pressure to the bladdersthrough vent tubes which pass through a reusable vacuum bag at locationsoutside of area of the bag that overlies the parts being cured. Thenumber of penetrations of the bag for venting purposes is reduced byventing more than one bladder through each vent tube. The manifoldsystem may comprise a plurality of removable manifold boxes arrangedend-to-end that may be reconfigured to suit the number of bladdersrequiring venting. Pre-loading of the vent tubes is avoided, andpotential distortion of fibers and/or resin starvation is substantiallyreduced, or eliminated

According to one disclosed embodiment, apparatus is provided forautoclave curing composite stiffeners against a composite skin. Theapparatus comprises a tool having a tool surface on which a compositeskin may be placed, and at least one channel adapted to have a compositestiffener placed therein beneath the skin; at least one pressurizablebladder adapted to be placed inside the channel for reacting autoclavepressure applied to the stiffener; a vacuum bag adapted to be sealedover the tool for compacting the skin against the stiffener; and amanifold system coupled with the bladder for pressurizing the bladderusing autoclave pressure, the manifold system including a vent tubepassing through the vacuum bag and exposed to autoclave pressure. Thebag may be a reusable bag and is attached to the frame. The bladderincludes a vent fitting on one end thereof, and the manifold system iscoupled with the vent fitting. The manifold system includes a manifoldbox, and the vent tube is mounted on the manifold box and coupled withthe vent fitting. The manifold box includes a top wall located beneathand in contact with the vacuum bag when the vacuum bag is sealed overthe tool, and the vent tube passes through the top wall. The apparatusmay further comprise a seal between the vacuum bag and the vent tube.The manifold system and the vent tube are located along a side of thetool, and the vacuum bag is adapted to be sealed to the vent tube.

According to another embodiment, an apparatus is provided for autoclavecuring of a plurality of composite stiffeners and a composite skin. Theapparatus comprises a tool adapted to have a composite skin placedthereon, the tool including a plurality of channels therein, each of thechannels adapted to have a composite stiffener placed therein andcontact with the skin. The apparatus further comprises a bag adapted tobe placed over the skin and exposed to autoclave pressure for compactingthe skin against the stiffeners, and a plurality of bladdersrespectively adapted to be placed within the stiffeners for reactingautoclave pressure applied to the stiffeners through the vacuum bag. Theapparatus also includes a manifold system located along one end of thetool channels and disposed beneath the bag for coupling the bladderswith autoclave pressure. The manifold system includes a manifold boxhaving a top wall adapted to be engaged by the bag, a vent tube passingthrough the top wall of the manifold box and through the bag, and linescoupling the vent tube with ends of the bladders. The apparatus mayfurther comprise a seal between the vent tube and the bag for sealingthe bag to the vent tube, as well as a frame, and clamps for clampingthe periphery of the bag between the tool and the frame. The manifoldsystem is located inside of the sealed periphery of the bag. Each of thebladders is elongate and includes a vent fitting on one end thereof, andthe manifold system is releasably coupled with each of the ventfittings. The manifold system includes a plurality of manifold boxesarranged end-to-end and each having a top, a plurality of vent tubesrespectively passing through the tops of the manifold boxes and throughthe bag. The vent tubes are coupled with ends of the bladders and aresealed to the bag.

According to still another embodiment, a method is provided of co-curingcomposite stiffeners and a skin within an autoclave. The methodcomprises placing the uncured stiffeners on a tool, placing bladdersrespectively in the uncured stiffeners, placing an uncured skin over thetool and in contact with the stiffeners, coupling the bladders with amanifold, sealing a bag over the tool and the manifold, venting themanifold to autoclave pressure through the bag, and pressurizing thebladders using autoclave pressure through the manifold. Coupling thebladders with the manifold includes coupling the ends of the bladderswith a vent tube exposed to the autoclave pressure. Sealing the bagincludes sealing the bag around the vent tube. Coupling the bladderswith the manifold includes coupling the ends of multiple ones of thebladders with the vent tube. Sealing the bag includes placing a frameover the bag and the tool, and clamping the bag between the frame andthe tool. The manifold may include a plurality of manifold boxes and themethod may further comprise placing the manifold boxes end-to-end on thetool and along one end of the bladders, and coupling each of themanifold boxes with a plurality of the bladders.

According to still further embodiment, a method is provided ofdistributing the pressure applied to composite parts during autoclavecuring of the parts. The method comprises placing the composite parts ona tool, placing bladders within the parts to react autoclave pressure,arranging multiple manifold boxes along one side of the tool, couplingeach of the manifold boxes to at least one of the bladders, sealing avacuum bag over the tool and the manifold boxes, and venting each of themanifold boxes through the vacuum bag. Venting each of the manifoldboxes through the vacuum bag includes passing vent tubes through thevacuum bag and sealing each of the vent tubes to the vacuum bag.Coupling each of the manifold boxes to at least one of the bladdersincludes using a quick disconnect to connect a manifold line to a ventinlet fitting on the bladder.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeembodiments are set forth in the appended claims. The illustrativeembodiments, however, as well as a preferred mode of use, furtherobjectives and advantages thereof, will best be understood by referenceto the following detailed description of an illustrative embodiment ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a top perspective view of a stiffenedcomposite skin.

FIG. 2 is an illustration of a bottom perspective view of the stiffenedskin shown in FIG. 1, revealing stiffeners that are co-cured with theskin in an autoclave.

FIG. 3 is an illustration of a perspective view of a hat type stiffenerthat may be used to stiffen the skin shown in FIGS. 1 and 2.

FIG. 4 is an illustration of a portion of a blade type stiffener.

FIG. 5 is an illustration of a functional block diagram of apparatus forco-curing a skin and stiffeners in an autoclave.

FIG. 6 is an illustration of a top perspective view of one embodiment ofthe apparatus shown in FIG. 5.

FIG. 7 is an illustration of a bottom perspective view of the apparatusshown in FIG. 6, the tool and tool base not shown for clarity.

FIG. 8 is an illustration of a sectional view taken along the line 8-8in FIG. 6.

FIG. 9 is an illustration of a top perspective view of a tool formingpart of the apparatus shown in FIGS. 5-8.

FIG. 10 is an illustration of a bottom perspective view of the apparatusshown in FIGS. 5-8, also showing the tool.

FIG. 11 is an illustration of an exploded perspective view of the bottomtool shown in FIG. 10.

FIG. 12 is an illustration of a perspective view of an array ofstiffeners used to stiffen the skin shown in FIGS. 1 and 2.

FIG. 13 is an illustration of a perspective view of an array of bladdersrespectively placed in the stiffeners shown in FIG. 12 during autoclavecuring.

FIG. 14 is an illustration of a perspective, end view of one of thebladders shown in FIG. 13, illustrating the bladder vent fitting.

FIG. 15 is an illustration of a perspective view of the apparatus, theframe and vacuum bag removed for clarity to reveal the location of thestiffeners and the bladders.

FIG. 16 is an illustration of a perspective view of one of the manifoldboxes forming part of the manifold system.

FIG. 17 is an illustration of a sectional view taken along the line17-17 in FIG. 16.

FIG. 18 is an illustration similar to FIG. 16, but showing the cover ofthe manifold box having been removed, the connecting hoses for thefittings not shown for clarity.

FIG. 19 is an illustration of a sectional view taken along the line19-19 in FIG. 6, the connecting hoses between the fittings not shown forclarity.

FIG. 20 is an illustration of an isometric view of a portion of one ofthe manifold boxes with the cover removed to reveal a vent tube and twoadjoining manifold fittings.

FIG. 21 is an illustration of a flow diagram of a method of co-curing acomposite skin and stiffeners in an autoclave.

FIG. 22 is an illustration of a flow diagram of aircraft production andservice methodology.

FIG. 23 is an illustration of a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring first to FIGS. 1 and 2, the disclosed embodiments relate to amethod and apparatus for fabricating a fiber reinforced, compositelaminate skin 30 stiffened with composite laminate stiffeners 32 whichare co-cured with the bottom side 34 of the skin 30. As will bediscussed below in more detail, the skin 30 and the stiffeners 32 arelaid up and formed to shape, as required, and then co-cured in anautoclave (not shown in FIGS. 1 and 2). The stiffeners 32, sometimesreferred to as stiffener ribs, may be any of several well-known types.For example, as shown in FIG. 3, the stiffeners 32 may be a hat shapedstiffener 32 having a hat section 36 and a flange section 38 that isattached to the bottom side 34 of the skin 30 during the co-curingprocess. FIG. 4 illustrates another type of stiffener 32 a referred toas a blade stiffener 32 a having a blade or web section 40 and a flangesection 38.

Referring now to FIG. 5, the skin 30 and the stiffeners 32 may beco-cured in an autoclave 44 using an apparatus generally indicated bythe 42. The apparatus 42 broadly comprises a tool 46 over which areusable vacuum bag 48 may be sealed. The tool 46 is configured to havea plurality of uncured composite stiffeners 32, sometimes referred to asstiffener charges, placed therein. A bladder 52 is placed inside each ofthe stiffeners 32 in order to react compaction pressure applied by theautoclave 44 and by the vacuum bag 48. An uncured composite skin (notshown in FIG. 5) is placed on the tool 46, overlying and in contact withthe flange sections 38 of the uncured stiffeners 32. A vacuum system 63coupled with the apparatus 42 is used to draw a vacuum within the vacuumbag 48 in order to draw the vacuum bag down against the skin 30,compacting the skin 30 against the flange sections 38 (FIGS. 3 and 4) ofthe stiffeners 32 during the curing process. In order to vent thebladders 52 to the autoclave pressure so that the bladders 52 to do notcollapse, a manifold system 54 is coupled 47 with each of the bladders52. The manifold system 54 includes one or more manifold boxes 57 whichmay be arranged end-to-end along one side 65 of the tool 46, spacedslightly from the ends of the bladders 52. Each of the manifold boxes 57is positioned beneath the vacuum bag 48 during a curing cycle, andincludes a vent tube 56 that extends upwardly through the vacuum bag 48at a location that is outside of the boundaries of the tool 46. The venttubes 56 extends into the environment of the autoclave 44, allowingautoclave pressure to be internally applied to the bladders 52; in otherwords, the manifold system 54 equalizes the pressure between environmentof the autoclave 44 and the internal volume of the bladders 52.

Attention is now directed to FIGS. 6, 7, 8 which illustrate additionaldetails of the apparatus 42. The apparatus 42 broadly comprises a frameassembly 50 to which a reusable vacuum bag 48 is attached. The vacuumbag 48 may comprise, for example and without limitation, an elastomer orother material that may withstand repeated pressure cycling and reuse.The frame assembly comprises a generally rectangular outer frame 53formed of rigid material such as a metal, and reinforcing cross framemembers 51 attached to the outer frame 53. The vacuum bag 48 may beattached to the outer frame 53 and covers the entire area of both thetool 46 and the manifold system 54.

The frame assembly 50 may also include handles 59 as well as clamps 58around the periphery of the outer frame 53. The handles 59 allow theframe assembly 50, along with the vacuum bag 48, to be manually liftedaway to permit loading and unloading of the skin 30 and the stiffeners32 (not shown in FIGS. 6-8). The outer frame may be also provided withguides 62 order to aid assembly alignment when the frame assembly 50 islowered down over the tool 46 (FIG. 5). As best seen in FIG. 8, thevacuum bag 48 includes a peripheral flat bag edge that is adapted to beclamped against a tool base plate 68 by a clamping plate 67 forming partof the frame assembly 50. Actuation of the clamps 58 load the outerframe 53 against the tool 46, thus clamping plate 67 against theperipheral flat bag edge 64 to create a vacuum tight seal between thevacuum bag 48 and the tool 46.

The vent tubes 56 are arranged along one side of the vacuum bag 48 andpass upwardly through openings in the vacuum bag 48 defined by circular,vent tube ring seals 60. The vent tube ring seals 60 slidably receivethe vent tubes 56 when the frame assembly 50 is lowered down onto thetool 46 in preparation for a curing cycle, and form a substantiallyvacuum tight peripheral seal between the vacuum bag 48 and the venttubes 56. In some embodiments, it may be possible to orient the venttubes 56 downwardly such that they do not penetrate the vacuum bag 48.One or more vacuum line fittings 66 may be provided to connect theinterior of the vacuum bag 48 with a suitable vacuum system 63 (FIG. 3)in order to evacuate the vacuum bag 48, causing the vacuum bag 48 to bedrawn down against the tool 46 and the manifold boxes 57.

FIGS. 9, 10 a and 11 illustrate additional details of one typical formof the tool 46 shown in FIG. 5. The tool 46 includes a tool billet 70and an underlying tool base plate 68 that is attached to the tool billet70, as by welding or other suitable techniques. The tool billet 70 maycomprise a solid piece of material, such as metal in which channels 74may be formed, as by machining. The channels 74 each have across-sectional shape corresponding to a portion of the stiffener 32,such as the hat section 36 of the stiffener 32. The tool billet 70 alsohas an upper tool surface 72 against which the flange section 38 of thestiffener 32 rests, along with the skin 30.

As shown in FIG. 10, the tool base plate 68 may include a plurality oftool base plate openings 76 therein which, in the illustrated exampleare generally rectangular in shape. The tool base plate openings 76allow access to the bottom side of the tool billet 70 and allow air tocirculate around the backside of the tool billet 70 in order to promotemore even heating/cooling, as well as quicker heat up and cool down ofthe tool 46. The tool base plate 68 provides the tool billet 70 with therequired rigidity, allowing a thinner tool billet 70 to be used whichmay reduce material costs and tool weight. However, in otherembodiments, a tool base plate may not be required where the tool billet70 is sufficiently thick to provide the required rigidity. FIG. 10 alsoreveals the placement of vacuum lines 78 through the tool base plate 68which are coupled with the vacuum line inlet fittings 66 and top of thetool billet 70 to allow evacuation of the vacuum bag 48.

As previously mentioned, preformed, uncured stiffeners 32 are placed inthe channels 74 of the tool billet 70, in preparation for a curingcycle. In the case of the stiffened skin 30 shown in FIGS. 1 and 2, thetool billet 70 is loaded with an array of uncured stiffeners 32, asshown in FIG. 12. FIG. 13 illustrates a corresponding array of bladders52 that are respectively placed in the uncured stiffeners 32 which havebeen previously seated in the channels 74 of the tool billet 70.Generally, the bladders 52 will have a cross-sectional shape and lengththat substantially match that of the uncured stiffeners 32. In someapplications, depending upon the configuration of the part assembly, thevarious ones of the stiffeners 32, along with the bladders 52 may havediffering cross-sectional shapes and/or lengths. FIG. 14 illustrates oneof the bladders that has a generally square cross-sectional shape suitedto form the hat section 36 of the stiffener 32 shown in FIGS. 2 and 3.As previously mentioned, the bladder 52 may be formed of a generallyflexible, impermeable material such as an elastomeric rubber. Each ofthe bladders 52 includes a bladder vent fitting 80 which may form partof a quick disconnect adapted to releasably connect the bladders 52 withthe manifold system 54 (FIG. 5).

FIG. 15 illustrates the tool 46 supported on a tool base 81, withuncured stiffeners 32 having been loaded into the channels 74 of thetool billet 70, with bladders 52 placed inside of the stiffeners 32.Each of the manifold boxes 57 includes manifold fittings 82 that arecoupled with the bladder vent fittings 80 (FIG. 14), with each other andwith a vent tube 56 by later discussed air lines or hoses (not shown inFIG. 15). As can be seen in this Figure, the manifold boxes 57,including the manifold fittings 82 and the vent tubes 56 are locatedalong one side of the tool 46, at one end of the bladders 52, beneaththe vacuum bag 48 when the frame assembly 50 is installed over the tool46.

Attention is now directed to FIGS. 16-19 which illustrate additionaldetails of one of the manifold boxes 57. The manifold box 57 may beformed of any suitable rigid material, such as sheet metal, and has agenerally open interior. When arranged end-to-end, end walls 90 of themanifold boxes 57 are positioned side-by-side. As best seen in FIGS. 16and 17, the manifold box includes a substantially flat top wall 84, andan outer, inclined sidewall 88. The top wall 84 includes a vent tubeopening 86 through which a vent tube 56 extends upwardly beyond the topwall 84. As previously mentioned, however, the vent tube 56 may extenddownwardly through the bottom of the manifold box 57 and the tool base81 (FIG. 15), thereby avoiding penetration of the vacuum bag 48. The topwall 84 and the inclined sidewall 88 may be of one-piece construction,or may be separate pieces, and are each removable to allow servicepersonnel to access the open interior of the manifold box 57. As bestseen in FIGS. 18 and 19, the manifold box 57 may further include aplurality of longitudinally spaced, stiffening ribs 98.

As best seen in FIGS. 17, 19 and 20, the vent tube 56 is mounted on avent tube base 100 which has a generally open interior and is providedwith fittings 95 that may be connected to fittings 82 by suitable hosesor airlines 102, as shown in FIG. 20. As can be seen in FIGS. 18 and 19,the manifold box 57 has sidewall openings 94 facing the tool 46 whichpermit the fittings to be connected to the vent fittings 80 on eachbladder 52 using the quick disconnects 96. The quick disconnects 96allow each of the manifold boxes 57 to be disconnected from the bladders52. Once disconnected, one or more of the manifold boxes 57 may beremoved, as necessary in order to reconfigure the manifold system 54 tosuit the particular part assembly to be cured. For example, thestiffened skin shown in FIGS. 1 and 2 employ four of the manifold boxes57 arranged end-to-end in order to deliver autoclave pressure to thebladders 52 (FIG. 13) placed in the corresponding stiffeners 32 (FIG.12). In the event that a stiffened skin 30 requires a fewer number ofthe stiffeners 32 (thus requiring fewer of the bladders 52), one or moreof the manifold boxes 57 may be removed simply by lifting them away fromthe tool base 81 (FIG. 15).

The apparatus 42 described above may be employed to co-cure skins 30 andstiffeners 32 in an autoclave using the method shown in FIG. 21.Beginning at step 104, preformed, uncured composite laminate stiffeners32 are placed on a tool 46, following which bladders 52 are placed inthe stiffeners 32 at 106. Next, at 108, an uncured composite laminateskin 30 is placed over the tool 46, and brought into contact with thestiffeners 32. At step 110, each of the bladders 52 is coupled with amanifold system 54 that is capable of supplying autoclave pressure tothe bladder 52. Next, at step 112, a vacuum bag 48 is sealed over thetool 46 and over the manifold system 54. The vent tubes 56 pass throughand are sealed to the vacuum bag 48. At step 114, the bladders 52 arevented to autoclave pressure through the vacuum bag 48 using themanifold system 54. At step 126, the bladders 52 are pressurized usingautoclave pressure delivered through the vent tubes 56.

Embodiments of the disclosure may find use in a variety of potentialapplications, particularly in the transportation industry, including forexample, aerospace, marine, automotive applications and otherapplication where autoclave curing of composite parts may be used. Thus,referring now to FIGS. 22 and 23, embodiments of the disclosure may beused in the context of an aircraft manufacturing and service method 94as shown in FIG. 22 and an aircraft 120 as shown in FIG. 23. Aircraftapplications of the disclosed embodiments may include, for example,without limitation, curing of stiffeners and stiffened skins such as,without limitation beams, spars stringers and wing skins, to name only afew. During pre-production, exemplary method 118 may includespecification and design 122 of the aircraft 120 and materialprocurement 124. During production, component and subassemblymanufacturing 126 and system integration 128 of the aircraft 120 takesplace. Thereafter, the aircraft 120 may go through certification anddelivery 130 in order to be placed in service 132. While in service by acustomer, the aircraft 120 is scheduled for routine maintenance andservice 134, which may also include modification, reconfiguration,refurbishment, and so on.

Each of the processes of method 118 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 23, the aircraft 120 produced by exemplary method 118may include an airframe 136 with a plurality of systems 138 and aninterior 140. Examples of high-level systems 138 include one or more ofa propulsion system 142, an electrical system 144, a hydraulic system146, and an environmental system 148. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of thedisclosure may be applied to other industries, such as the marine andautomotive industries.

Systems and methods embodied herein may be employed during any one ormore of the stages of the production and service method 118. Forexample, components or subassemblies corresponding to production process126 may be fabricated or manufactured in a manner similar to componentsor subassemblies produced while the aircraft 120 is in service. Also,one or more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 126 and 128, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 120. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft120 is in service, for example and without limitation, to maintenanceand service 34.

The description of the different illustrative embodiments has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the embodiments in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art. Further, different illustrativeembodiments may provide different advantages as compared to otherillustrative embodiments. The embodiment or embodiments selected arechosen and described in order to best explain the principles of theembodiments, the practical application, and to enable others of ordinaryskill in the art to understand the disclosure for various embodimentswith various modifications as are suited to the particular usecontemplated.

1. An apparatus for autoclave curing composite stiffeners against acomposite skin, comprising: a tool having a tool surface on which acomposite skin may be placed, and at least one channel adapted to have acomposite stiffener placed therein beneath the skin; at least onepressurizable bladder adapted to be placed inside the channel forreacting autoclave pressure applied to the stiffener; a vacuum bagadapted to be sealed over the tool for compacting the skin against thestiffener; and a manifold system coupled with the bladder forpressurizing the bladder using autoclave pressure, the manifold systemincluding a vent tube passing through the vacuum bag and exposed toautoclave pressure.
 2. The apparatus of claim 1, further comprising: aframe, and wherein the bag is a reusable bag and is attached to theframe.
 3. The apparatus of claim 1, wherein: the bladder includes a ventfitting on one end thereof, and the manifold system is coupled with thevent fitting.
 4. The apparatus of claim 3, wherein the manifold systemincludes: a manifold box, and wherein the vent tube is mounted on themanifold box and coupled with the vent fitting.
 5. The apparatus ofclaim 4, wherein: the manifold box includes a top wall located beneathand in contact with the vacuum bag when the vacuum bag is sealed overthe tool, and the vent tube passes through the top wall.
 6. Theapparatus of claim 5, further comprising a seal between the vacuum bagand the vent tube.
 7. The apparatus of claim 1, wherein: the manifoldsystem and the vent tube are located along a side of the tool, and thevacuum bag is adapted to be sealed to the vent tube.
 8. Apparatus forautoclave a plurality of composite stiffeners and a composite skin,comprising: a tool adapted to have a composite skin placed thereon, thetool including a plurality of tool channels therein, each of the toolchannels adapted to have a composite stiffener placed therein andcontact with the skin; a bag adapted to be placed over the skin andexposed to autoclave pressure for compacting the skin against thestiffeners; a plurality of bladders respectively adapted to be placedwithin the stiffeners for reacting autoclave pressure applied to thestiffeners through the bag; and a manifold system located along one endof the tool channels and disposed beneath the bag for coupling thebladders with autoclave pressure.
 9. The apparatus of claim 8, whereinthe manifold system includes: a manifold box having a top wall adaptedto be engaged by the bag, a vent tube passing through the top wall ofthe manifold box and through the bag, and lines coupling the vent tubewith ends of the bladders.
 10. The apparatus of claim 9, furthercomprising: a seal between the vent tube and the bag for sealing the bagto the vent tube.
 11. The apparatus of claim 8, further comprising: aframe; and clamps for clamping the periphery of the bag between the tooland the frame.
 12. The apparatus of claim 11, wherein the manifoldsystem is located inside of the periphery of the bag.
 13. The apparatusof claim 8, wherein: each of the bladders is elongate and includes avent fitting on one end thereof, and the manifold system is releasablycoupled with each of the vent fittings.
 14. The apparatus of claim 9,wherein the manifold system includes: a plurality of manifold boxesarranged end-to-end and each having a top, a plurality of vent tubesrespectively passing through the tops of the manifold boxes and throughthe bag, and wherein the vent tubes are coupled with ends of thebladders and are sealed to the bag. 15-23. (canceled)